This invention relates to a heat-stabilizing composition for proteins and protein-containing emulsions. The invention also relates to the heat-stabilized product.
Egg yolk is a natural emulsifier commonly used in the preparation of sauces and mayonnaises. However, its commercial use in food products is limited by its tendency to coagulate at relatively low temperatures (65.degree. C.), which results in destabilization of the oil-in-water emulsion followed by a heavy exudation of oil. As a result of this, compositions containing natural egg yolk break up when they are sterilized or when they are heated to their boiling point.
Great Britain Complete Patent Specification No. 1,525,929 relates to a water-in-oil emulsion containing a phospholipoprotein (for example egg yolk) modified with phospholipase A (PLA). This emulsion is stable if it is treated for 30 minutes at 100.degree. C. However, the major disadvantage is that the egg yolk is enzymatically modified, and the elimination of PLA activity by proteases is not possible because the proteolytic enzyme would modify the proteins of the egg yolk and the PLA on its own could only be deactivated at very high temperatures (160.degree. C.).
European patent application No. 91 121 318.9 filed by applicants on Dec. 12, 1991 relates to a water-in-oil emulsion containing an exogenous lysophospholipid (LPL) emanating from soya. The LPL is prepared from a lecithin fraction with a relatively high content of phosphatidyl choline (PC) which is converted by PLA into lysophatidyl choline (LPC). The PLA is then deactivated by addition of a protease of which the enzymatic activity is reduced by heat treatment. The disadvantage of this solution is that it involves the use of a lecithin fraction rich in PC to obtain a sufficiently high level of LPC. Now, on the one hand, the cost of such a fraction is relatively high and, on the other hand, the procedure involves an additional stage for inactivating PLA. In addition, the presence of free fatty acids in the substrate enzymatically hydrolyzed in situ can impart a taste to the end product.